tonight the clock is ticking on u.S. Military action in syria. The white house says a decision is near and u.S. War ships are in position. And the rest of the world is also joining the debate about what kind of action and exactly when. The goal, to stop a man using brutal chemical weapons 5,000 miles away. Abc's martha raddatz has it all from the milt ooez. Reporter: He is the man at the center of this horror. A brutal dictator who has been responsible for gassing his own people. There is no doubt who is responsible for this heinous use of chemical weapons in syria. The syrian regime. Reporter: Tonight there seems no question that the u.S. Is ready to strike a punishing blow to assad. U.S. War ships are in place, cruise missiles at the ready, the targets in syria selected. You're ready to go like that? We're ready to go like that. Reporter: What might assad do in response? The syrian regime has hundreds of tons of mustard gas and stock piles of sarin. Add to that 100,000 missiles and rockets including thousands of powerful scud missiles which could reach any neighboring target in israel. Today in israel a run on gas masks, questions increasing four forward. Prime minister benjamin netanyahu says we are ready and we will respond in strength. There is no one stronger in this region. Nuclear armed israel has the most advanced ballistic missiles, cruise missiles and missile defense systems making assad believe they would be crazy to try to hit israel. It might create an opportunity for israel that they would be glad to take advantage of and perhaps assad would rue the day this he gave them this opportunity. Reporter: But if he's madman enough to reign chemicals down on his people knowing the possible consequences there is no telling what he would do if cruise missiles reign down on his regime. Martha joins me from jerusalem. Are they going to target him? They're not going to target him, they've's made a point of that but certainly military targets in his regime. That's got to make his nervous. I remember meeting him and interviewing him. I should remind everybody he grew up a lot of his life in london. He's a physician, educated there. Why wouldn't they target him? What do they expect from him next? I think they're afraid of reaction and they don't want regime change. The administration has been very clear about that. This is a limited strike. It's only to prevent any further chemical attacks. They don't want to get involved in this civil war but it must be extraordinary for you as you say this man educated in london doing this brutal things. He's someone who never expected to take over from his father. Thank you so much, martha raddatz again reporting from jerusalem tonight.

This transcript has been automatically generated and may not be 100% accurate.

Snipers Take Aim at UN Weapons Inspectors in Syria

Searching for evidence of deadly chemical attacks could force America to respond.

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